Primary Prevention in Infants of Mothers Who Have Asthma

The National Asthma Campaign Manchester Asthma and Allergy Study (NACMAAS)

Article Citation(s):
Custovic A, Simpson BM, Simpson A, Kissen P, Woodcock A. Effect of environmental manipulation in pregnancy and early life on respiratory symptoms and atopy during first year of life: A randomized trial. Lancet 2001; 358:188-93.

Program Description:
This prenatal study investigation sought to determine whether stringent environmental manipulation could prevent sensitization and allergic disease in children at high risk for atopy. Investigators hypothesized that reduced exposure to allergens might offer a realistic opportunity for primary prevention of atopy and asthma. Couples who agreed to take part were allocated to risk groups according to their atopic status, history of allergic disease, and pet ownership. The first two groups included couples in which both parents were atopic, the mother was sensitized to indoor allergens, and no cat or dog was in the house. The first group was a stringent environmental manipulation group, the intervention group, and the second was a high-risk control group. The third group was a high-risk pet group where both parents were skin-test positive, and they had a cat and/or a dog. The fourth group, the low-risk group, had parents who were both skin-test negative, had no history of atopic disorders, and had no pets. Interventions for the intervention group included covering the maternal bed (pillow, mattress, and quilt) with allergen impermeable bedding during pregnancy and after delivery, use of a high-filtration vacuum cleaner, removal of carpets in the infants’ room and replacement with a vinyl floor, and provision with new custom-made cot and carrycot mattresses encased in allergen-proof material during the manufacturing process. Participants were asked to wash their infant’s linen in hot water once a week, and benzyl benzoate was applied to carpets and soft furnishings throughout the rest of the house.

The follow-up clinical and subsequent home visits were identical in all four groups of infants. Parents and children were invited into the clinic within 2 weeks of the child’s first birthday. An interviewer administered a standard questionnaire, and a physical examination was completed to identify the presence of respiratory symptoms or eczema, or both, in children and the use of medication. The severity and frequency of wheeze and wheeze with shortness of breath were assessed, and the medications used to treat wheezy attacks were documented. Skin-prick tests for six common allergens were conducted (D pteronyssinus, cat, dog, mixed grasses, milk, and egg).

Evaluation Design:
A randomized cohort approach was used.

Sample Size:
A total of 517 people participated in the four study groups

Outcome Measures/Results:
Signs and symptoms of atopic disease at age 1 year for children born to study couples were the outcome measures. Children in the high-risk intervention group were less likely than those in the high-risk control group to have respiratory symptoms during the first year of life. The most pronounced differences were in the relative risks for severe wheeze with shortness of breath: relative risk 0.44 (95% confidence intervals 0.2-1.00), prescribed medication for the treatment of wheezy attacks: relative risk 0.58 (95% CI 0.36-0.95), and wheezing after vigorous playing, crying, or exertion; relative risk 0.18 (95% CI 0.04-0.79). The probability of respiratory symptoms in the high-risk control group and high-risk pet group infants was similar; however, it was much lower in the low-risk than in the high-risk control group. Cat ownership was significantly associated with sensitization to cats. These findings support a dose-response relation between exposure to cat and specific sensitization, at least in early life. Dog ownership was not associated with either sensitization to cats or dogs. The protective effect of environmental manipulation was limited to respiratory symptoms, and the relative risks for other symptoms suggestive of atopic disorder (eczema and allergies to food) were almost identical in the three groups of high-risk infants.